What is the value of the expression $(25 + 8)^2 - (8^2 +25^2)$?
Explanation: Expanding the left square, we see that the given expression equals $25^2 + 2\cdot25\cdot8 + 8^2 - 8^2 - 25^2 = 2\cdot25\cdot8 = \boxed{400}$.